Abstract
A wide variety of AC/DC power converter topologies have been developed in order to improve the system efficiency, input power factor and system redundancy for stationary battery energy storage systems. Due to the nature of high-power batteries, there is a big voltage difference between battery terminals from the end of discharge to the high charge value. To prevent unregulated battery voltages from harming the system loads, several techniques are used in the industry. A well-known old technique named as diode dropper is simple but suffers from low efficiency. Using a DC-DC converter is more advantageous, although it increases the cost. In this paper, the use of partial power processing converters which attract interest these days has been proposed as an alternative. The proposed full bridge/push-pull series connected partial power converter has a slight modification compared to the classical one presented in the literature. A system with 22 kW power rating was designed and tested. In order to compare the results, a two-switch buck-boost converter was also designed and tested for the same conditions. The results show that the proposed converter is superior to both the two-switch buck-boost converter and other topologies in terms of efficiency and response speed. Efficiencies of 97%–99% have been attained with the proposed converter.
Highlights
Battery energy storage system (BESS) has become very widespread in the last decade
In Zientarski et al.,[18] three 750-W prototypes; one fullbridge phase-shifted series partial-power converter (FB/PS S-Partial power converters (PPCs)), one fly-back S-PPC, and one fullpower converter were compared, and the results show that the FB/PS S-PPC topology achieves the highest efficiency in DC-DC conversion, while the fly-back topology does not behave like a partial power processing converter as expected
It can be seen from these values and graphics that proposed FB/PP S-PPC has higher efficiency than two-switch buck-boost converter (TSBBC) in all various test conditions, especially in equal input and output voltages condition due to series-voltage regulator ability
Summary
Battery energy storage system (BESS) has become very widespread in the last decade. lithium-based batteries are preferred in many applications such as portable devices and electric vehicles, lead-acid batteries and Ni-Cd batteries are still preferred in several applications in industry such as power plants, uninterruptable power supplies, SCADA-monitoring systems, DC substation systems, electrical vehicles, aircrafts and telecom applications. Due to the nature of the charge–discharge characteristics of batteries there is a large variation of voltage at the battery terminals in a complete charge discharge period.[1,2,3,4,5,6,7] To protect DC loads from this unregulated voltage, many special designs are implemented such as diode droppers, DC-DC converters or float cum boost chargers.[8,9]. Processing only part of the rated power instead of the full power supplied to the load has been proposed to improve the performance of converters.[10,11] Partial power converters (PPCs) using this concept have been proposed for use with photovoltaic (PV) systems.[12,13,14,15,16] Among different approaches, full bridge push pull series connected PPC
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